As we all know, the field of pharmacovigilance has grown enormously in recent years. Some of this was caused by normal expansion at pharmaceutical companies and at biotechnology firms through the addition of new products and in pioneering fields. Perhaps the most compelling source of growth in the pharmacovigilance area has been through FDA requirements regarding the reporting of adverse events and other unexpected outcomes. There are many persons who see a continuing increase in the importance and size, especially in headcount, for a pharmacovigilance component of these companies. However, there is some reason to believe that new developments in the area of personalized medicine may change much of that expected progression. If we step back and think about the causes of adverse events and other untoward reactions to medications, we find that many of these are due to various metabolic pathways that differ both in group populations as well as within individuals.